Hi
We went to Cork for the day in May. We took a bus ride from Cork into Kinsale, and is definately worth visiting. It is beautiful, the views are stunning, we walked along the harbor and out on the costal path even though it was wet and miserable I couldn't believe what a beautiful place it was. The walk we took was called the Scilly walk (the local bus driver told us all about it on way into Kinsale) and you can walk right round the bay to Charles Fort, but stop off for a pint at the Bullman pub on the way! if you type in Kinsale Scilly walk into google there are loads of websites.
I'm not a great walker but would definately recommend this.
Enjoy your stay in Cork!